BGP - The Protocol
Network reachability is announced with so-called AS-Pathes, describing the path to the final network through intermediate ASes
A BGP speaker usually announces directly connected networks, and prefixes with their pathes it learned from its neighbors
An AS Path looks like "13237 174 3602 22512", listing the AS numbers we cross on the way to the destination, in this case, cvs.openbsd.org